Boost Spike
03-16-2009, 02:26 PM
#27
yes it does...
i mostly see the spike at WOT in higher gears 4th 5th 6th when the rpm's hit 5.5-6k.
greddy type RS BOV...i fee its decent.
hmm...good info...
i have to double check where my boost is reading off tonight.
but see today is warm...about 60 degrees here in Chicago and i had no spike while driving. boost stayed at about 6psi.
greddy type RS BOV...i fee its decent.
I've done a lot of experimenting with this in the last few days and discovered a problem most people with boost controllers wont even know they have .
Boost surge under partial throttle at mid to high rpm .
You will only notice this if you have your pressure guage on the turbo side of the throttle body. I was seeing 15psi here while the UIM is still in vacuum .
The fix is easy - plug your boost controller into the turbo side of the throttle and not into the uim as most people do .
Boost surge under partial throttle at mid to high rpm .
You will only notice this if you have your pressure guage on the turbo side of the throttle body. I was seeing 15psi here while the UIM is still in vacuum .
The fix is easy - plug your boost controller into the turbo side of the throttle and not into the uim as most people do .
i have to double check where my boost is reading off tonight.
but see today is warm...about 60 degrees here in Chicago and i had no spike while driving. boost stayed at about 6psi.
03-16-2009, 02:31 PM
#28
Boosted!!!
Join Date: Apr 2008
Location: Puerto Rīco
Posts: 960
Likes: 0
Received 0 Likes
on
0 Posts
Of course it depends on the wastegate. If it cant let go enough pressure your psi will build up. That was the problem I was having. when I got past 6k the pressure would just build up to about 10psi because the wastegate could not dump it fast enough.
03-16-2009, 02:43 PM
#29
/\ I have never seen this happen so I'm not sure why others would have this issue when I have the same wastegate .
Are you saying that you saw the boost go up to 10psi ish at WOT from 6k ? What happened from then on ?
The only spkie i get is between gear changes and I thought this was what people were talking about .
Are you saying that you saw the boost go up to 10psi ish at WOT from 6k ? What happened from then on ?
The only spkie i get is between gear changes and I thought this was what people were talking about .
Last edited by Brettus; 03-16-2009 at 02:54 PM.
03-16-2009, 02:51 PM
#30
Boosted!!!
Join Date: Apr 2008
Location: Puerto Rīco
Posts: 960
Likes: 0
Received 0 Likes
on
0 Posts
yep it happened every single time. I dont know what happened then on because I always shifted at a litte more than 6k since the power died after that according to the dyno I had done. I read in some forum that it could have been from my exhaust because that would help it boost creep. This is normal on some turbos.
03-16-2009, 03:02 PM
#31
man - no wonder you upgraded . But your experience is nothing like mine - I do have the upgraded compressor wheel but I'm pretty sure nothing has been done to the wastegate and I have never had that issue .....
I'm seeing very good power all the way to 8500 and shift at around 7700
I'm seeing very good power all the way to 8500 and shift at around 7700
Last edited by Brettus; 03-16-2009 at 03:05 PM.
03-16-2009, 03:12 PM
#32
Boosted!!!
Join Date: Apr 2008
Location: Puerto Rīco
Posts: 960
Likes: 0
Received 0 Likes
on
0 Posts
yeah but that is thanks to your upgraded compressor wheel. If I knew I could get good results with just that I would have just upgraded my turbo instead of buying a new one.
03-16-2009, 03:59 PM
#33
If your AccessPORT tuning is done (or even close), you should be able to handle the fueling for spikes like that with no problem.
The problem is that, at the torque peak, there is a sudden increase of exhaust pressure which spools the turbo very quickly.
Depending on throttle position, the wastegate may or may not open in time to manage the pressure.
The problem is that, at the torque peak, there is a sudden increase of exhaust pressure which spools the turbo very quickly.
Depending on throttle position, the wastegate may or may not open in time to manage the pressure.
03-17-2009, 12:39 PM
#36
tuning and fuel is good...
I usually just shift if it starts going to 10psi...but AFR is on the money.
but I would like to be able to set the boost to my liking and use an open exhaust and not worry about a spike.
how many people have ventured into the world of external wastegates??
i know someone did here and i seen the pics.
I usually just shift if it starts going to 10psi...but AFR is on the money.
but I would like to be able to set the boost to my liking and use an open exhaust and not worry about a spike.
how many people have ventured into the world of external wastegates??
i know someone did here and i seen the pics.
03-17-2009, 01:22 PM
#37
Registered User
iTrader: (2)
Join Date: Oct 2008
Location: Dallas, Texas
Posts: 726
Likes: 0
Received 0 Likes
on
0 Posts
Well i am no expert when it comes to boosting 8's however i have built and designed several turbo kits for my other vehicles and i will say this. For all the other vehicles i have built kits for i have used External WG's and never had boost spike issues.... However i did make a turbo kit for a Spec V and the owner really wanted a internal WG do to his engine bay setup and piping issues. I warned of boost spike however he didnt think it would be a big issue but he constantly gets it and will most likely need a engine rebuild in the near future. Whenever i turbo my 8 (if i decide not to go SC) then i will be making my own exhaust manifold with an externally gated setup.
Bov's very very rarely can even contribute to boost spike. Many higher HP cars dont even run BOV's because their turbo's are made to handle the surge and they dont get the boost spike yall are talking about.
I also think that rotary vehicles are more prone to it because of the fact that they run richer then most vehicles and unburnt fuel is sent into the exhaust. This unburnt fuel apon hitting the hot collector and turbo manifold will combust and create added pressure spooling the turbo.
Bov's very very rarely can even contribute to boost spike. Many higher HP cars dont even run BOV's because their turbo's are made to handle the surge and they dont get the boost spike yall are talking about.
I also think that rotary vehicles are more prone to it because of the fact that they run richer then most vehicles and unburnt fuel is sent into the exhaust. This unburnt fuel apon hitting the hot collector and turbo manifold will combust and create added pressure spooling the turbo.
03-17-2009, 02:20 PM
#40
Boosted!!!
Join Date: Apr 2008
Location: Puerto Rīco
Posts: 960
Likes: 0
Received 0 Likes
on
0 Posts
the thing that makes it happen is exhaust, do a search on boost creep and boost spikes in google and read on the subjetct. Most if not all the people that have it happen is because of massive free flowing exhausts with internat wastegates on the turbo. When it started happening to me I started reading around and leaned a bit on what the problem could be.
03-17-2009, 03:08 PM
#41
Yeay Boosted!
Thread Starter
Join Date: Oct 2007
Location: New Hampshire
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
so.. your saying I Turbo XS exhaust might be the reason? 
since it's one of the biggest free flowing exhausts around?
Well, I think a meth kit will probibly ease alot of worry from the boost spikes. Now I'm wondering if I should have really bothered putting in my blocking plate for the greddy..
since it's one of the biggest free flowing exhausts around? Well, I think a meth kit will probibly ease alot of worry from the boost spikes. Now I'm wondering if I should have really bothered putting in my blocking plate for the greddy..
Last edited by marcux; 03-17-2009 at 03:11 PM.
03-17-2009, 04:07 PM
#43
Yeay Boosted!
Thread Starter
Join Date: Oct 2007
Location: New Hampshire
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
I guess somtimes freeflowing isn't always better. I'm willing to bet, alot of people with the freeflowing exhausts are the ones getting those boost spikes
03-17-2009, 11:04 PM
#46
marcux - also read this just in case it is relevant ....
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/where-did-you-plumb-your-boost-controller-into-uim-no-good-169316/
https://www.rx8club.com/series-i-major-horsepower-upgrades-93/where-did-you-plumb-your-boost-controller-into-uim-no-good-169316/
03-18-2009, 02:00 AM
#47
Registered User
iTrader: (2)
Join Date: Oct 2008
Location: Dallas, Texas
Posts: 726
Likes: 0
Received 0 Likes
on
0 Posts
The exhaust is the prime reason you have the boost spikes which is why the external Wastegate is needed. Ill explain the reasoning.
Ok a XS turbo exhaust is a full 3" all the way back giving you NO backpressure. This is exactly what you want when boosted however there is a fault with the internal WG design and a freeflowing exhaust.
Wastegates are designed so that when they open the air follows the path of least resistance and would normally go through that tiny hole instead of spinning the turbine wheel and then exiting. Well when you have a free flowing exhaust there really is no resistance so when the Internal gate is opened the smaller hole is temporarily creating more resistance then the air flowing through the turbine wheel which causes it to continue spooling.
Now, this normally is not the problem when you have an exhaust with some back pressure because the back pressure in the exhaust causes the turbine wheel to want to surge and the path of least resistance becomes the small open hole that the internal wastegate provides.
This can still happen with an external wastegate that is plumbed back into the exhaust but because of the size of external wastegates this is extremely rare but can still happen under certain circumstances which is why the best setup is a External Wastegate that has its own dump. No boost creep/spike and the sound of the open dump wastegate is amazing
Ok a XS turbo exhaust is a full 3" all the way back giving you NO backpressure. This is exactly what you want when boosted however there is a fault with the internal WG design and a freeflowing exhaust.
Wastegates are designed so that when they open the air follows the path of least resistance and would normally go through that tiny hole instead of spinning the turbine wheel and then exiting. Well when you have a free flowing exhaust there really is no resistance so when the Internal gate is opened the smaller hole is temporarily creating more resistance then the air flowing through the turbine wheel which causes it to continue spooling.
Now, this normally is not the problem when you have an exhaust with some back pressure because the back pressure in the exhaust causes the turbine wheel to want to surge and the path of least resistance becomes the small open hole that the internal wastegate provides.
This can still happen with an external wastegate that is plumbed back into the exhaust but because of the size of external wastegates this is extremely rare but can still happen under certain circumstances which is why the best setup is a External Wastegate that has its own dump. No boost creep/spike and the sound of the open dump wastegate is amazing
03-18-2009, 05:04 AM
#49
Yeay Boosted!
Thread Starter
Join Date: Oct 2007
Location: New Hampshire
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
ok, that makes me feel so much better, you guys rock. I was worried because my turbo guy was noticing all the spikes to 10. and he didn't understand why we went through the who system a couple of times, checking all the lines and making sure the wastegate was opening at the right pressure.. never thought it just might have been my exhaust..
I'm just going to run it at 10 psi and be happy
I'm just going to run it at 10 psi and be happy
03-18-2009, 10:41 AM
#50
yeah when i put back the stock midpipe i noticed much more steady spool....but i do miss my open midpipe.
has anyone here set the greddy internal wastegete actuator rod to run more than the stock 5-6 psi.
i want to crank it up to 10 psi using just the actuator rod...just wondering if people still had spikes with that.
obviously it would be better with a boost controller but JW.
great discussion so far guys,
has anyone here set the greddy internal wastegete actuator rod to run more than the stock 5-6 psi.
i want to crank it up to 10 psi using just the actuator rod...just wondering if people still had spikes with that.
obviously it would be better with a boost controller but JW.
great discussion so far guys,